The present invention relates to a binocular with an interpupillary adjustment mechanism.
There is a known binocular having an interpupillary adjustment mechanism. A recently developed binocular has two (left and right) casings respectively accommodating left and right telescope systems, and the left casing is slidably supported by the right casing so that the interpupillary distance can be adjusted by sliding the left casing with respect to the right casing.
In such a binocular, as the interpupillary distance increases, the amount of the left casing pulled out of the right casing increases. That is, a hollow portion (that has been occupied by the left casing) is increased in the right casing. Accordingly, the strength (i.e., rigidity) of the right casing is decreased, which also decreases the strength of the binocular as a whole.